The invention relates to a valve unit having an overridable check valve, a valve housing, on which a first and second fluid power connection are provided, which are connected by way of a power duct on which a check valve is placed, which may be overridden by a fluid control signal, said signal being able to be supplied by way of a signal input connection of the valve housing.
Furthermore, the invention relates to a fluid power drive fitted with two such valve units.
The German patent publication 8,804,229 U1 discloses a valve unit of this type, which is designed for connection with a fluid operated drive in the form of a fluid power cylinder. By way of the first power connection a power fluid may be supplied, which flows through the check valve in order to move same in the one direction. For the drive to operate in the opposite direction as well, the power fluid must be free to flow out through the valve unit, something which is made possible by mechanical overriding of the overridable check valve. For this purpose a fluid control signal is supplied by way of the signal input connection.
Normally a power cylinder is simultaneously fitted with two such valve units, the fluid signal to be supplied to the respectively one valve unit being tapped. In this fluid duct for this purpose it is conventional to use a T-union, which permits tapping of the fluid control signal.
One object of the invention is to reduce the degree of technical complexity involved for installation of a valve unit containing an overridable check valve.
In order to achieve these and/or other objects appearing from the present specification, claims and drawings, in the present invention in the case of a valve unit of the type initially mentioned there is a provision such that the valve housing is additionally provided with a signal output connection connected with the power duct.
A fluid operated drive is conveniently fitted with two valve units designed on these lines, the signal output connection of the respectively one valve unit being connected by way of fluid duct with the signal output connection of the respectively other valve unit.
This all means that the design complexity in connection with providing the fluid control signal and in connection with reducing the number of the components required is less. The fluid control signal required for an other valve unit may be tapped immediately at the signal output connection, which is in the form of a permanent component of the valve unit and accordingly does not have to be fitted separately. In the case of a fluid operated drive fitted with two valve units of this type there is hence a considerable reduction in the amount of assembly work and an extremely compact arrangement may be realized.
Further advantageous developments of the invention are defined in the claims.
It is convenient for the check valve to be so designed that in the absence of a control signal it permits fluid flow from the first to the second power connection and in the opposite direction turns off flow, the signal output connection being connected with the power duct""s section running between the first power connection and the overridable check valve. In this design optimum response behavior is possible, since the control signal is made available even before the overridable check valve is opened by the pressure of the supplied operating fluid.
An other preferred feature of the invention is such that between the first power connection and the corresponding check valve there is in addition a choked check valve, which may be utilized in order to provide for speed control of the connected drive. If the check valve is for instance so designed that it permits fluid flow to the overridable check valve and prevents flow in the opposite direction, the valve unit may perform the task of choking the flow of spent air. In a similar manner choking of the input air flow is possible, if the turn off direction of the check valve is reversed.
If a choked check valve is present, the signal output connection is preferably connected with the power duct""s section extending between the first power connection and the choked check valve.
The valve unit may in principle have an integral or one-piece valve housing. In the case of a preferred design of the invention however a multi-part structure is provided having a pivot part mounted for rotary motion on a principal body of the valve housing, preferably not only the first power connection but also the signal output connection being formed jointly on the pivot part.
The second power connection of the valve unit preferably serves for the connection to the housing of a fluid power drive, such drive being provided if desired with a screw thread which permits connection by screwing in place. The first power connection on the contrary is preferably designed for detachable connection with a fluid duct by way of which the operating fluid may be supplied and let off.
The first power connection, the signal input connection and the signal output connection may more especially be fitted respective with plug connection means, which permit releasable connection by plugging of a fluid duct.
Particularly compact dimensions and optimum access may be provided for if the first power connection and the signal output connection are aligned to be parallel and alongside one another in their arrangement.
Further advantageous developments and convenient forms of the invention will be understood from the following detailed descriptive disclosure of embodiments thereof in conjunction with the accompanying drawings.